Carbon steels and alloy steels for cold forging

ABSTRACT

This invention relates to machine structural carbon steels and alloy steels having an excellent cold forging property. Such a steel can be produced by deoxidizing a carbon steel or an alloy steel with a calcium-silicon alloy and controlling the calcium content thereof.

United States Patent Ito et al. 1451 Mar. 28, 1972 [541 CARBON STEELS AND ALLOY STEELS [56] 1 Cited FOR COLD FORGING UNITED STATES PATENTS [72] 939 Nagm 3,000,731 9/1961 Ototani ..7s/129 3,212,881 10/1965 Dunn ....7s/5s x [73] Assignee: Daido Seiko Kabushiki Kaisha, Aichi Pre- 3,215,525 1965 Spr e ----7 3 X fecture, Ja a 3,275,433 9/1966 Hilty ....75/58 X 3,309,194 3/1967 Dunn ....75/58 X [221 F1led= 'v 1968 2,258,604 10/1941 Gagnebin ..75/123 x l A l. N 761463 [2 1 pp 0 Primary Examiner--L. Dewayne Rutledge Assistant Examiner-Joseph E. Legru [30] Foreign Application Priority Data Attomey-Wenderoth, Lind & Ponack Oct. 11, 1967 Japan "42/6495? ABSTRACT [52] us Cl /123 L 75/123 R 75/126 G This invention relates to machine structural carbon steels and [51] Int Cl u wczzc 39/00 alloy steels having an excellent cold forging property. Such a 58 Field Jiiii..........IIZ55/58 1 2 3 1 29 123 L 123 R be Pmduced by dwxidizing a Steel steel with a calcium-silicon alloy and controlling the calcium content thereof.

6 Claims, 3 Drawing Figures PATENTEnIIIIRze I972 3,652,267

6 I00 I3 E 89 cum I J1 9O (Z LP I: 6 0 I I I I CALCIUM CONTENT BY WEIGHT (x) .FIG.I

5 5 90- 5 m a a; 80* g t II U 70 I I I I I SIOC, 520C 530C 845C 5550 TEST SAMPLES 2 m) I62 0 I00 5 DE 0 m 9O 25; Q I: 55 8O SCM3 SCM3 DEOXIDIZED DEOXIDIZVED WITHA WITH CALCIUM ALUMINUM ALLOY INVENTORS TETSURO ITO H63 AZUMA HIKI BY 5Z4 ATTORNEYS CARBON STEELS AND ALLOY STEELS FOR COLD FORGING This invention relates to machine structural carbon steels and alloy steels which can be cold forged and are produced by tsshlqrsh qndjz tby-usiing ga minum. The m pieces as in FIG. 1 were made and the test pieces were subjected to the thermal treatment for spheroidizing annealing them and then they were tested for the critical reduction in deoxidizing carbon Steels and alloy Steels with a .height in the same manner as in FIG. 1. It is obvious from the icon alloy. Particularly, this invention relates to machine structural carbon steels and alloy steels having an excellent cold forging property and containing calcium in an amount varying from 0.0015 percent to 0.0060 percent by weight.

Heretofore, it was reported by H. Opitz and others that the machine structural carbon steel designated as 845C steel becomes to have a better machinability after it was deoxidized by using a calcium-silicon alloy such as Ca Si or CaSi than that of the 8450 steel which was deoxidized by using alminium or silicon. Also it was reported by Hasegawa and others that stainless steels become to have good hot workability after they were deoxidized by using a calcium alloy.

In the course of the investigation for improving the machinability of the machine structural carbon steels and alloy steels, we have found the new fact that their cold forging property is remarkably improved when they are deoxidized by using a calcium-silicon alloy such as Ca si or CaSi and the calcium content retained therein is controlled to the range varying from 0.0015 percent to 0.0060 percent by weight.

This invention is fully explained by referring to the accompanying drawings in which:

FIG. 1 shows a curve illustrating the relationship between the calcium content and the critical reduction in height for initiating the visible surface crack of machine structural carbon steel designated as 545C steel in the Japanese Industrial Standards after it was deoxidized by using a calcium-silicon alloy which contains calcium in an amount varying from percent to percent by weight and silicon in an amount varying from percent to percent by weight. It is noted that the critical reduction in height is calculated by the following equation.

wherein Ho indicates the initial height of the test piece and H 4 indicates the final height of the test piece ofter it was compressed. The test piece has the size of 6mm. in diameter and; 12mm. in height, and it was polished with a grinder. The test piece was compressed at the speed of 5mm. per minute. The test was conducted for 20 test pieces and the critical reduction 4 in height is given as the average value.

As it is obvious from FIG. 1, the maximum value of the critical reduction in height is obtained at the point indicating the calcium content of 0.0025 percent by weight.

curves (1) and (II) as shown in FIG. 2 that the steels which were deoxidized with the calcium alloy have better cold forging property than that of the steels which were deoxidized with aluminum.

FIG. 3 shows a curve illustrating the critical reduction in height of machine structural alloy steel designated as SCM3 steel in the Japanese Industrial Standards after it was deoxidized by using the calcium-silicon alloy as in FIG. 1 and the calcium content retained therein was controlled to 0.0025 percent by weight and also the steel was deoxidized by using the metallic aluminum and the aluminum content retained therein was controlled to 0.019 percent by weight, and then each steel was tested for the critical reduction in height in the same manner as in FIG. 1. It is obvious from the curve as shown in FIG. 3 that the steel which was deoxidized with the calcium-silicon alloy has better cold forging property than that of the steel which was deoxidized with aluminum in spite of the presence of the alloying components such as Cr and Mo.

Examples of the cold forging carbon steels and alloy steels achieved in accordance with this invention and the control examples are summarized in the following Table.

The various steels referred to in the present application are designated according to the Japanese Industrial Standards and are cold forgeable carbon steels having the following compositions:

810C steel: 0.08 to 0.13 percent carbon, 0.15 to 0.35 percent silicon, 0.30 to 0.60 percent manganese and the balance being substantial iron and incidental impurities.

S200 steel: 0.18 to 0.23 percent carbon, 0.15 to 0.35 percent silicon, 0.30 to 0.60 percent manganese and the balance being substantially iron and incidental impurities.

S30C steel: 0.27 to 0.33 percent carbon, 0.15 to 0.35 percent silicon, 0.60 to 0.90 percent manganese and the balance being iron and incidental impurities.

545C steel: 0.42 to 0.48 percent carbon, 0.15 to 0.35 percent silicon, 0.60 to 0.90 percent manganese and the balance being iron and incidental impurities.

SSSC steel: 0.52 to 0.58 percent carbon, 0.15 to 0.35 percent silicon, 0.60 to 0.90 percent manganese and the balance being iron and incidental impurities.

SCM3 steel: 0.33 to 0.38 percent carbon, 0.15 to 0.35 percent silicon, 0.60 to 0.85 percent manganese, 0.90 to 1.20 percent chro'mium, 0.15 to 0.30 percent molybdenum, and the FIG. 2 shows two curves illustrating the critical reduction in 50 balanee being substantially iron and incidental impurities.

Chemical component Steels C Si Mn P S Cr Mo Ca A1 S100 deoxidized with a 0a-a11oy 0.11 0.31 0.48 0.018 S100 deoxidized with aluminium 0.09 0.29 0. 52 0.020 S200 deoxidized with a Ca-alloy 0. 22 0. 33 0.40 0.014 S200 deoxidized with alumlnium- 0. 22 0. 24 0.43 0.016 S300 deoxidized with a Ca-aIloy. 0.32 0.32 0.70 0.013 S300 deoxidized with aluminium 0. 29 0. 30 0. 71 0.019 S450 deoxidized with a Ca-alloy. 0.43 0. 28 0. 73 0.019 S450 deoxidized with aluminium. 0.43 0.31 0.71 0.019 S550 deoxidized with a Ca-alloy 0.56 0.25 0.78 0.014 S550 deoxidized with aluminum 0.54 0.29 0.72 0.018 SCM3 deoxidized with a 0a-a1loy- 0. 36 0.31 9.75 0. 014 0.014 1.94 0.23 0.0025 SCM3 deoxidized with aluminium 0.35 0.28 0. 71 9.017 0.011, 1.01 0.21 0.0001 0.019

height for initiating the visible surface crack of machine struc- 65 We claim:

tural carbon steels designated as 8100 steel, S200 steel, S300 steel, 845C steel and 555C steel in the Japanese Industrial Standards after they were deoxidized by using a calcium alloy or aluminum and the calcium or aluminum content retained in 1. A cold forgeable carbon steel, characterized in that a steel consisting essentially of 0.08 to 0.13 percent of carbon 0.15 to 0.35 percent of silicon, 0.30 to 0.60 percent of manganese and the balance substantially iron and incidental imputhem was controlled to an amount varying from 0.0022% Ca 'rities is deoxidized with a calcium-silicon alloy and controlled to Al Ca by weight or from 0.016% al. to 0.028% A1 by weight. The curve (I) shows the critical reduction in height when the above-mentioned steels were deoxidized by using the calcium-silicon alloy as in FIG. 1 and the curve (11) shows so as to contain calcium in an amount varying from 0.0015 to 0.0060 percent.

2. A cold forgeable carbon steel, characterized in that a steel consisting essentially of 0.18 to 0.23 percent of carbon,

the critical reduction in height when the above-mentioned 0.15 to 0.35 percent of silicon, 0.30 to 0.60 percent of man- .so as to contain calcium in an amount varying from 0.0015 to 0.0060 percent.

4. A cold forgeable carbon steel, characterized in that a steel containing 0.42 to 0.48 percent of carbon, 0.15 to 0.35;

percent of silicon, 0.60 to 0.90 percent of manganese and the balance substantially iron and incidental impurities is deoxidized with a calcium-silicon alloy and controlled so as to contain calcium in an amount varying from to 0.0060 percent.

5. A cold forgeable carbon steel, characterized in that a steel consisting essentially of 0.52 to 0.58 percent of carbon,

0.15 to 0.35 percent of silicon, 0.60 to 0.90 percent of manganese and the balance substantially iron and incidental impurities is deoxidized with a calcium-silicon alloy and controlled so as to contain calcium in an amount varying from 0.0015 to 0.0060 percent.

6. A cold forgeable Cr-Mo base steel, characterized in that a steel consisting essentially of 0.33 to 0.38 percent of carbon,

0.15 to 0.35 percent of silicon, 0.60 t0.0.85 percent of manganese, 0.90 to 1.20 percent of chromium, 0.15 to 0.30 percent of molybdenum and the balance substantially iron and incidental impurities is deoxidized with a calcium-silicon alloy and controlled so as to contain calcium in an amount varying fron 1 0 .0015 to 0.0060 percent. 

2. A cold forgeable carbon steel, characterizEd in that a steel consisting essentially of 0.18 to 0.23 percent of carbon, 0.15 of 0.35 percent of silicon, 0.30 to 0.60 percent of manganese and the balance substantially iron and incidental impurities is deoxidized with a calcium-silicon alloy and controlled so as to contain calcium in an amount varying from 0.0015 to 0.0060 percent.
 3. A cold forgeable carbon steel, characterized in that a steel consisting essentially of 0.27 to 0.33 percent of carbon, 0.15 to 0.35 percent of silicon, 0.60 to 90 percent of manganese and the balance substantially iron and incidental impurities is deoxidized with a calcium-silicon alloy and controlled so as to contain calcium in an amount varying from 0.0015 to 0.0060 percent.
 4. A cold forgeable carbon steel, characterized in that a steel containing 0.42 to 0.48 percent of carbon, 0.15 to 0.35 percent of silicon, 0.60 to 0.90 percent of manganese and the balance substantially iron and incidental impurities is deoxidized with a calcium-silicon alloy and controlled so as to contain calcium in an amount varying from 0.0015 to 0.0060 percent.
 5. A cold forgeable carbon steel, characterized in that a steel consisting essentially of 0.52 to 0.58 percent of carbon, 0.15 to 0.35 percent of silicon, 0.60 to 0.90 percent of manganese and the balance substantially iron and incidental impurities is deoxidized with a calcium-silicon alloy and controlled so as to contain calcium in an amount varying from 0.0015 to 0.0060 percent.
 6. A cold forgeable Cr-Mo base steel, characterized in that a steel consisting essentially of 0.33 to 0.38 percent of carbon, 0.15 to 0.35 percent of silicon, 0.60 to 0.85 percent of manganese, 0.90 to 1.20 percent of chromium, 0.15 to 0.30 percent of molybdenum and the balance substantially iron and incidental impurities is deoxidized with a calcium-silicon alloy and controlled so as to contain calcium in an amount varying from 0.0015 to 0.0060 percent. 